Henrik Ducharme has a special bond with his little sister, six-month-old Madalayna. After today, they'll be even closer.

The two-year-old is giving some of his bone marrow to his tiny sister in a hospital in Toronto today, according to a post by their mother Tamara on the Miracle for Madalayna Facebook page.

The Windsor baby, called a Warrior Princess by her family, was born with malignant infantile osteopetrosi — a rare genetic disorder that can cause infections, hearing and vision loss and even death.

"We made it this far and she is still giving us smiles once in a while," Tamara wrote. "She is losing her voice her cry makes us sad. She sounds like the wind blowing through cracks of the windows."

The family has been warned the next few weeks will be the hardest, and asked online for prayers Madalayna's "little" body" will accept the marrow and that no complications will arise. They asked for prayers for their "hero" Henrik too.

"I couldn't figure out how to tell him what is in his future tomorrow," Tamara posted, adding that she cried as she tried to explain what was happening to her son. "All I told him was that he will be helping his sister and he said he wants to help Madalayna."

At least 1,300 people in Windsor came out to get swabbed and see if they could help Madalayna. No perfect match was found, but her mother wrote in another post that Henrik was the best match from the family.

Still, doctors were worried as the disease is genetic and he could be carrying a similar mutation or even have the disease.

Further genetic testing found no mutations and once doctors in Toronto had consulted colleagues around the world they decided to move forward as quickly as possible.

On Friday morning Tamara wrote that her daughter was sleeping while Henrik and husband checked into the hospital.

She thanked everyone for their support and asked for continued prayers.